1. Field of the Invention
The present invention relates to a multilayer electronic component having internal circuit elements arranged therein, and more particularly, it relates to an improvement in forming external electrodes in a multilayer electronic component.
2. Description of the Background Art
A multilayer electronic component, which is represented by a multilayer capacitor, a multilayer inductor, a multilayer circuit board or a multilayer composite electronic component, for example, comprises a laminate which is obtained by stacking a plurality of insulating sheets with interposition of internal circuit elements such as conductor films and/or resistor films. The insulating sheets are typically prepared from ceramic sheets.
FIG. 15 shows a conventional multilayer electronic component 1 in which a laminate 2 is obtained by stacking a plurality of insulating sheets with interposition of internal circuit elements (not shown). The laminate 2 is provided on its four side surfaces, for example, with respective external electrodes 3. These external electrodes 3 are electrically connected with the internal circuit elements which are located in the interior of the laminate 2. The external electrodes 3 are formed by applying suitable metal paste to specific positions of the respective side surfaces of the laminate 2. Portions of the external electrodes 3 extend to the upper and lower surfaces of the laminate 2 as seen in FIG. 15.
FIG. 16 shows another type of conventional multilayer electronic component 4, which also comprises a laminate 5 that is obtained by stacking a plurality of insulating sheets with interposition of internal circuit elements (not shown). The laminate 5 is provided on its four side surfaces, for example, with external electrodes 6 which are electrically connected with the internal circuit elements. These external electrodes 6 are formed by dividing through holes 7, as shown by phantom lines in FIG. 16. Namely, a mother laminate is prepared so that a plurality of multilayer electronic components 4 can be obtained when the mother laminate is cut along prescribed cutting lines. The through holes 7 are formed in the mother laminate and conductor films are formed on inner peripheral surfaces thereof for defining the external electrodes 6. The mother laminate is thereafter cut to divide the through holes 7. Due to the method of forming the conductor films for the external electrodes 6 in such a multilayer electronic component 4, parts of the external electrodes 6 extend to the upper and lower surfaces of the laminate 5.
These multilayer electronic components 1 and 4 are surface-mounted on suitable circuit boards through the external electrodes 3 and 6 in the form of chips.
In both of the aforementioned multilayer electronic components 1 and 4, however, the external electrodes 3 and 6 extend toward the upper and lower surfaces of the laminates 2 and 5. Therefore, when other components are to be mounted on the upper and/or lower surface(s) of such multilayer electronic components 1 and 4 to form a composite electronic component with the components 1 and 4, the areas available for mounting such components are restricted.
Further, the parts of the external electrodes 3 and 6 extending toward the upper and lower surfaces of the laminates 2 and 5 inhibit reduction of arrangement pitches for the external electrodes 3 and 6. In addition, it is relatively difficult to form such parts of the external electrodes 3 and 6 to have uniform sizes and shapes which further inhibits reduction of the arrangement pitches for the external electrodes 3 and 6.
More particularly, in the multilayer electronic component 4 shown in FIG. 16, it is difficult to reduce the diameters of the through holes 7, which are formed by a drill having a diameter of less than 0.3 mm. This also restricts the arrangement pitches for the external electrodes 6. Further, the drill for forming the through holes 7 has a relatively short life further increasing the cost of manufacturing the electronic component.
In the multilayer electronic component 1 shown in FIG. 15, the external electrodes 3 are formed on the four side surfaces of the laminate 2, respectively. Hence, it is necessary to perform four separate application steps for applying the metal paste onto the respective side surfaces. As a result, the number of steps for forming the external electrodes 3 is increased.
It is necessary to measure the electric characteristics of the multilayer electronic components 1 and 4 before shipping the components 1 and 4. In both of the multilayer electronics components 1 and 4, however, the electric characteristics cannot be measured unless the components 1 and 4 are in states that are similar to those when the components 1 and 4 are used as chips. In the multilayer electronic component 1 shown in FIG. 15, measurement of the electric characteristics is possible only after formation of the external electrodes 3. Also in the case shown in FIG. 16, the characteristics of each multilayer electronic component 4 cannot be measured while the component 4 is in the form of the mother laminate. Such measurement of the electric characteristics is possible only when the mother laminate is cut to divide the through holes 7.